1. Field of the Invention
This invention relates to a method of manufacturing a casing base for a hard disc drive device.
2. Description of the Prior Art
FIG. 5 shows an example of casing base for a hard disc drive device manufactured by die casting. This casing base is fabricated in the following steps.
(1) An eventual casing base 11 of aluminum is die cast. PA0 (2) Then, gas such as air remaining in cavities which has fatal adverse effects on the performance of hard disc is removed, and also contaminants due to rusting or like cause are removed. PA0 (3) Further, surface treatment with a chemical or surface coating is made in order to maintain the cleanness of the surface. PA0 (4) Subsequently, the work is machined to correct the shape and dimensions. PA0 (5) Finally, the work is washed to maintain the cleanness.
This process of manufacture has the following demerits.
(a) The process involves a large number of steps from the die casting till the completion. PA1 (b) It is necessary to provide means for avoiding the generation of cavities. PA1 (c) If cavities are generated, washing for removing oil and other contaminants that may get into the cavities can not be readily made, and it is difficult to maintain the cleanness. PA1 (d) A casting die is necessary, which is generally expensive. PA1 (e) This leads to an increased cost of manufacture. PA1 (a) The frames 13 which are press formed in advance, has a very complicated shape, and their fabrication requires a large number of press forming steps. PA1 (b) A step of mounting the frames 13 on the base 12 is necessary, and the mounting position and mounting strength are stringently restricted. PA1 (c) Consequently, a high cost of manufacture is inevitable.
Because of the difficulty of maintaining the cleanness, it is necessary to close the cavities by coating or carry out a surface treatment with a chemical to prevent rusting.
There is another method of manufacture as shown in FIGS. 6 and 7. In this case, an eventual casing base 12 of aluminum is formed with a recessed portion 14 using a press, and then frames 13 which have been press formed in advance are mounted on the opposite sides of the base 12.
This method, unlike the method based on the die casting of aluminum, is free from the problem of cavities and is advantageous from the standpoint of securing the cleanness.
This method, however, has the following demerits.